Transport pathways of black carbon to a high mountain Himalayan lake during late Holocene: Inferences from nitrogen isotopes of black carbon

Abstract

Historically, forest fires have played a significant role in the production and distribution of black carbon (BC), including its deposition in water bodies. BC can reach to water bodies through two main pathways: (i) wet and dry atmospheric deposition and (ii) transportation of soil BC via surface runoff. Identifying the transport pathways of BC after fire has proven to be a challenging endeavour. This study aimed to decipher the pathway of BC transportation to a lake (Wular Lake, Kashmir Valley, India) by utilizing nitrogen isotopic composition of BC (δ15NBC) from a sediment core spanning 3744 years. The δ15NBC record demonstrate that terrestrial N dynamics in the Kashmir Valley were predominantly influenced by shifts in climate condition during the late Holocene. The observed variations indicated lower δ15NBC, indicative of dominance of atmospheric transportation of BC to the lake, during relatively drier periods with higher forest fire activity. In contrast, higher δ15NBC, suggesting a dominance of soil BC transportation via runoff, aligned with relative wetter periods of low forest fire activity.